3
Swept and Displaced Volumes Swept Volume/cylinder: V s = swept volumed B = bore diameter s = stroke s s x A p Inlet Port Note: In valve design the Volume which flows into the cylinder must equal the volume which flows through the inlet port. The velocity past the valve must then be considerably greater than the velocity in the cylinder.

4
Port Sizing and Mach Index (Z) Mach Index is the ratio of the velocity of the gases flow area to the speed of sound D b = cylinder bore dia. D p = port dia. n = number of ports For mean values:

7
Modern performance engines will use multiple inlet and exhaust valves per cylinder. Many are using multiple intake runners per cylinder to improve cylinder filling over a broader range of RPM. –A single runner is used at lower RPM while a second runner will be opened at higher RPM. –The second and the combined each have their own tuning peak. Port Sizing and Mach Index (Z)

8
Inlet Air Density and Performance

9
Inlet air density Law of Partial Pressures: If each is considered as a perfect gas

29
Helmholtz Tuning Writing Clearance Volume in Terms of Compression Ratio: The Primary Volume is considered to be the Cylinder Volume with the Piston at mid-stroke (effective volume).

30
The tuning peak will occur when the natural Helmholtz resonance of the cylinder and runner is about twice the piston frequency. Volume (V 1 )= Cylinder Volume Volume (V 2 )= Volume in the path from V 1 to the Plenum Using Engelman's electrical analogy we can define the system as a system defined by capacitances and inductances. Helmholtz Tuning

31
The EFFECTIVE INDUCTANCE for a pipe with different cross-sections may be defined as the sum of inductances of each section. The INDUCTANCE RATIO (a) is defined as the ratio of the secondary inductance to the primary inductance. Helmholtz Tuning

37
A combined equation is possible indicating its 2 nd order Helmholtz Tuning

38
David Visards Rule of thumb Equations Using Visard's Equation for Runner Length 1. Starting point of 7 inches for 10,000 RPM 2. Add length of 1.7 inches for each 1000 RPM less Using Visard's Equation for Runner Diameter